1. Field of Invention
This invention relates to pentacoordinate silyl enolates and to their use as polymerization initiators for methacrylic monomers, including methacrylate esters.
2. Background
Noyori et al., J. Am. Chem. Soc. 99, 1265 (1977); ibid 102, 1223 (1980) have proposed, without experimental support, pentacoordinate silicon-containing species as reactive intermediates in the fluoride-catalyzed addition of silyl enol ethers to carbonyl compounds such as aldehydes. There is no disclosure of the spirosilicate structures of the invention which is the basis of this application, which invention will be described in detail hereinafter.
U.S. Pat. No. 4,447,628 discloses anionic pentacoordinate silicates of the formula ##STR1## wherein: R.sup.1 and R.sup.2 are both aryl or one is aryl and the other is C.sub.1-4 alkyl, or R.sup.1 and R.sup.2 taken together are ##STR2## Y is CF.sub.3 or, when R.sup.1 and R.sup.2 are taken together, CH.sub.3 ; X is F, CN or N.sub.3 when Y is CF.sub.3 ;
X is F when Y is CH.sub.3 ; PA1 M.sup..sym. is (R.sup.3).sub.4 N.sup..sym., [(R.sup.4).sub.2 N].sub.3 S.sup..sym. or Cs.sup..sym. when X is F; PA1 M.sup..sym. is (R.sup.5).sub.4 N.sup..sym. when X is CN; PA1 M.sup..sym. is [(R.sup.4).sub.2 N].sub.3 S.sup..sym. or (R.sup.5).sub.4 N.sup..sym. when X is N.sub.3 ; PA1 aryl is phenyl, phenyl substituted with F, C.sub.1-4 alkyl or C.sub.1-4 alkoxy, or naphthyl; PA1 R.sup.3 is C.sub.1-4 alkyl; PA1 R.sup.4 is C.sub.1-2 alkyl or (R.sup.4).sub.2 is (CH.sub.2).sub.5 ; and PA1 R.sup.5 is C.sub.2-4 alkyl. PA1 X is --C(O)X' or; PA1 X' is --OSi(R.sup.1).sub.3, --OR or --NR'R"; PA1 each R.sup.1, independently, is H or a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms; provided, however, at least one R.sup.1 is not H; PA1 R is a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms, optionally containing one or more ether oxygen atoms within aliphatic segments thereof, and optionally containing one or more functional substituents that are unreactive under polymerizing conditions; and PA1 each of R' and R" is independently selected from C.sub.1-4 alkyl, PA1 R.sup.4 is a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms, optionally containing one or more ether oxygen atoms within aliphatic segments thereof; and PA1 M is lithium, sodium, potassium or cesium, preferably lithium,
The silicates are useful as catalysts for the polymerization of methyl methacrylate in the presence of selected silicon-containing initiators such as [(1-methoxy-2-methyl-1-propenyl)oxy]trimethylsilane. Such initiators are described in greater detail in U.S. Pat. Nos. 4,417,034 and 4,414,372, as is their use in the presence of selected anion and Lewis acid catalysts for the polymerization of acrylic and methacrylic monomers.
Farnham et al., in J. Am. Chem. Soc. 103, 4608 (1981) discuss structural aspects of the anionic pentacoordinate silicon compounds of the formulae ##STR3##
Perrozzi et al. in J. Am. Chem. Soc. 101, 1591 (1979) disclose similar pentacoordinate silicon compounds of the formula ##STR4## wherein R is methyl or phenyl.
It is an object of this invention to provide pentacoordinate silyl enolates which initiate polymerization of methacrylic monomers, including methacrylate esters, in the absence of catalysts, unlike the tetracoordinate silicon initiators of the art which require catalysts.